The present invention relates generally to reconfigurable input devices. More particularly, the input device of the present invention utilizes tactile sensor technology while at the same time allowing the device to change its function depending on the needs of a particular application. In one particularly advantageous embodiment, the tactile input device is capable of measuring contact location and pressure in multiple locations simultaneously to increase the error-free processing of the commands. In another embodiment, tactile feedback is provided to the user upon compression of the sensor giving a confirmation of the successful completion of command input. Applications for the device of the present invention range from adaptable consumer products such as mobile phones, PDAs, portable audio and video players (such as Apple computer's popular iPod product line), and other portable electronic devices to industrial and robotics uses.
Two-dimensional (X,Y) reconfigurable input devices that measure the contact location on a display are commonly known. They comprise a contact matrix and detect the absence or presence of electrical signal in each cell of the matrix. Typically, these input devices are made clear such that they overlay a rigid output display. This configuration is excellent for use in large-sized screens where the display can show a large button that is not obstructed by the user's hand interacting with the input device.
However, for small, portable electronic devices, such as mobile phones and PDAs, the human finger is too large relative to the small-sized display. Because of this problem, many devices provide a small stylus to interact with the touch screen which takes more time to use, is difficult to handle, and is easily lost.
Another class of devices often used for input device is proximity sensors. These devices sense the presence of electrical conductive properties, such as found in a human fingertip, near the input device. However, they are susceptible to environmental changes and cannot work with non-conducting objects, such as a person wearing a glove. This class of devices does not measure contact pressure and therefore is not always able to interpret the intent of the user. Consequently, user interaction with these devices is limited.
Capacitance sensors have been known to be used as input devices, such as described in U.S. Pat. No. 4,736,191 by Matzke. This patent describes a touchpad made as a circular capacitance proximity sensor for use as a non-reconfigurable input device for a computer.
U.S. Pat. No. 5,463,388 by Boie describes a mouse or keyboard input device based on measuring capacitance changes due to the proximity effect of conductive and moist objects, such as the human hand, as an input device for computers.
U.S. Pat. No. 6,188,391 by Seely and U.S. Pat. No. 5,648,642 by Miller show another example of a two-layer capacitive touchpad made as a proximity sensor comprising conductive electrodes on opposite sides of a dielectric material. In a related patent, U.S. Pat. No. 5,841,078 by Miller, pressure sensing is discussed, but the approach shown is an indirect method of determining pressure based on the fingertip contact area increasing with increased pressure.
U.S. Pat. No. 6,888,536 by Westerman describes a sensor for simultaneously tracking multiple finger and palm contacts using an array of proximity sensors. This device is designed for handling multiple functions such as typing, cursor movement, and gesture recognition. The disclosed invention uses proximity sensors that require as many as 4 connections per sensor element and places the corresponding electronic circuit at the pixel level. Westerman describes the ability to measure both pressure and proximity effects, but fails to describe how the two effects can be decoupled.
Reconfigurable input devices based on an interchangeable keyboard and video display are also known in the art. U.S. Pat. No. 4,202,041 by Kaplow, for example, describes an input keyboard that dynamically changes the button appearance depending on the language and the functional requirements. Individual key buttons, however, are expensive to produce using conventional discrete electrical switches. U.S. Pat. Nos. 6,035,180 and 5,877,695 by Kubes describe an electro-luminescent (EL) driver encased in the electronics of a mobile device that drives a matrix array to display various warnings, patterns, and images. These patents mention placing a touch input device below the EL display, but do not specify the details of the touch sensor.
U.S. Pat. No. 6,888,537 by Benson describes an input device that sends as an output signal the contact location (X,Y) along with the applied force (Z) in combination with a printed configuration sheet that allow the switch to operate in different applications. The description of this invention shows a foam-like compressible material designed to work as a compliant dielectric material, but in practice this foam cannot be made thin enough for use as an input device in small, portable electronic devices.
U.S. Pat. No. 6,824,321 by Ward describes a generic X,Y touch sensor combined with a multi-layered EL display to enable it to function in multiple modes. The EL display is placed behind the touch sensor, requiring the touch sensor to be essentially clear. The touch sensor, however, can be confused by multiple-point contacts and does not provide contact force information.
Finally, U.S. Pat. No. 5,479,528 by Speeter describes using a tactile sensor and IC (Integrated Circuit) to identify the size of a user to thereby reposition a virtual input device, such as a keyboard and mouse, to an optimal location.
The need therefore exists for a reconfigurable input device which provides simultaneous position and pressure information over the entire surface of the sensor so as to provide better flexibility in designing Control User Interfaces (CUI). The need also exists for an input device capable of detecting the distinct location and pressure of a touch in multiple locations so as to improve error-free processing of the user's commands.